Thrombogenicity, a problem with long-term artificial lungs, is caused by blood-biomaterial interactions and is made worse by nonuniform flow, which also causes decreased gas exchange. To overcome these obstacles, we changed the inlet and added a uniform flow pump to our previous oxygenator design. Conventional membrane oxygenators have a ½-inch port for the inlet of blood. These port structures make it difficult for the blood to flow uniformly in the oxygenator. In addition, the complex blood flow patterns that occur in the oxygenator, including turbulence and stagnation, lead to thrombogenicity. A cross-flow pump (CFP) can result in uniform blood flow to the inlet side of an oxygenator. In this study, we evaluated the usefulness of an integrated oxygenator with a fiber bundle porosity of 0.6 and a membrane surface area of 1.3 m2. The inlet part of the oxygenator is improved and better fits the outlet of the CFP. Each of the three models of the improved oxygenator has a different inlet taper angle. The computational fluid dynamics analysis showed that, compared with the original design, uniform flow of the integrated oxygenator improved by 88.8% at the hollow fiber membrane. With the integrated oxygenator, O2 transfer increased by an average of 20.8%, and CO2 transfer increased by an average of 35.5%. The results of our experiments suggest that the CFP, which produces a wide, uniform flow to the oxygenator, is effective in attaining high gas exchange performance.